Electrical monitoring system



2 Sheets-Sheet 1 l Oct. l5, 1963 J.L. BARKER ELECTRICAL MONITORING SYSTEM Filed Jan. 6, 1959 Oct. l5, 1963 J. l.. BARKER ELECTRICAL MONITORING SYSTEM 2 Sheets-Sheet 2 Filed Jan. 6, 1959 l To l OTHER Loom.

CONTROLLERS 26Cdec.

CAM SEQUENCE INVENTOR.

JOHN L. BARKER PERIODS ATTORNEY United States Patent O P Filed llan. 6, 1959, Ser. No. 7555,258 16 Claims. (Ci. 340-41) This invention relates to electrical monitoring systems for the sensing of phase variation between two electrical signals, progressively shifting in phase with respect to each other, and is more particularly concerned with supervision of a master controller in a traffic control system through monitoring two sets of polyphase output control lines of the master controller to sense any cessation of such progressive phase shift, and to provide for emergency operation of the master controller and/or local controllers in the traffic control system in response to such sensing and give indication of such condition, as desired.

Certain traffic control systems are controlled by a master controller through its output including a pair of polyphase electrical systems, one polyphase system, sl-owly and progressively shifting in phase with respect to the other polyphase system for the purpose of .timing numerous remote local traffic signal controllers.

An example of such a trafic control system may be found in my copending applicati-on, Serial Number 510,926, filed May 25, 1955 under the name Control System, now iU.S. Patent 2,989,728 entitled Traffic and Other Control Systems.

Control over, and operation of multiple traflc controllers in such traffic control system depend on phase rotation between the two polyphase systems. Therefore, it is important to determine, as soon as possible that a failure of rotation has occurred or to automatically provide alternate power in the vent of such failure to provide continued control over or continued operation of the multiple local trafiic controllers in the traic control system. l

From one aspect of the present invention is a monitoring system which senses progressive phase shift of the individual phases of one three phase system with respect to a common representative phase of a second three phase system which, during normal operation of both three phase systems, is progressively shifting in phase with respect to the monitored three phase system, the monitor cooperating with an alternate source of supply control unit which unit is operable upon failure of rotation of one or more of the phases of the monitored three phase system over a timed and predetermined sequence of operation.

From another aspect of the present invention is a monitoring apparatus and indicating system, for monitoring the three phase systems of a master controller of a traffic control system which master controller employs two three phase systems shifting in phase with respect to each other for control of the local traffic controllers in the control system, with the monitoring apparatus controlling an indicator device and control device which, after a short delay supplies an alternate control system, or emergency control system to control the local control- 1ers ofthe traffic control system in the event of a continued failure of the normal control system, while simultaneously indicating the failure and the nature of the emergency actions taken, and upon continued failure of the control system to the local controllers, to release the individual local controllers from master control and permit the local controllers to operate as independent traffic controllers, while also indicating the same through visual and/or audible indicating devices.

From still another aspect the invention is a trafc 3, l @7,338 Patented Oct. 15, 1963 ICC control system supervisor designed to sense normal effective output of a master controller to local controlleis in a master controlled traffic control system, with provision for application of an alternate output to control the local controllers upon failure of normal output of the master controller three phase control systems, and upon continued failure of master control due to failure of the alternate output .to control the local controllers, to release master control over the local controllers in the traffic control system and permit the local controllers to operate as isolated independent trafiic controllers.

From a still further aspect the invention is a multiple polyphase electrical system monitor which senses the progressive phase shift between a pair of polyphase electrical systems, shifting in phase with respect to each other, in combination with testing apparatus initiated into a predetermined cycle `of operation by the monitor, after sensing failure of rotation, for testing and determining the general location of a failure of phase shift, with indicating means associated with the testing apparatus for indicating the presence of failure, the general location of failure relative to a predetermined component in the polyphase generating system, and for indicating the remedial action taken by way of application of an alternate source of power as controlled by the testing apparatus.

Itis an object of the invention to continuously monitor phase rotation between two polyphase electrical output systems of a master controller in Ia traffic control system, which polyphase systems are progressively shifting in phase with respect to each other, and upon sensing a failure of phase rotation between the two polyphase systems to reconnect certain parts of the master controller of the traffic control system to emergency equipment to secure the best emergency operation.

Another object is to maintain the monitoring of two polyphase electrical output signals of a master controller in a traic control system and determine the effect of the output of emergency .equipment on the trafiic control system and to give indication of such effect.

A further object is to indicate the presence of a failure in the output of a master control system and to indicate what remedial steps have automatically been taken to provide emergency operation.

An additional object is to release the local controllers of a traffic control system from master control in the event that restitution of phase rotation between the two polyphase output systems of the master controller of the traffic control system has not taken place after application of the output of emergency equipment.

It is another object to provide monitoring apparatus responsive to phase rotation between two polyphase systems to initiate test .apparatus into `a predetermined cycle including an initial delay of the -test and remedial action to avoid response to a momentary interruption 1of power.

Still another object is to provide testing apparatus with an initial delay in its cycle of operation to provide for accumulation of multiple momentary interruptions of power or multiple momentary failures of phase rotation between two polyphase outputs of a master controller in a trafc control system which polyphase outputs are continuously monitored.

Another object is to provide for the sensing of a failure of phase rotation between t-wo polyphase outputs of a master controller without having to fwait a period greater than the longest cycle of operation of the traic control system before remedial measures are taken.

It is a further yobject to recheck the output of a master controller in the event that failure of the output has been the fault of a power failure or power line interruption.

'Ihese and other objects will be apparent yfrom a reading rciated drawings.

FIG. l is a block diagram of a traic control system including a Imaster control station employing the present invention, hereinafter referred to as a SYSTEM SUPER- VISOR, in cooperation with the units of a lmaster controller with control lines to a local controller. A local controller is illustrate-d las controlling trahie signals at one intersection in a traffic controlsystem. k

FIG. 2 is a circuit diagram of the preferred embodiment of the present invention with the two three phase lines illustrated at the top of the'diagram, three monitoring circuits individually blocked oi and a relay network below the monitoring circuits inclu-ding `a motor, associated cam contacts and indicating devices and alarms.

' FIG. 3 is a cam sequence chart that may be associated Y with the cam contacts illustrated in FIG. 2.

Referring now to FIG. l, the block diagram of the traiic control system includes a master control station, marked 'off on three sides by a broken line, the two three phase control lines, extending from the master control station to one of the local controllers of the traffic control system and extending to other local controllers, and one local controller with an intersection represented below the local controller with signal lights kcontrolling the intersection controlled by the local controller. It should be understood that additional local controllers controlling other intersect-ions would be connected to the two three phase control lines in a manner similar to the connections illustrated `for the local controller here shown.

The MASTER CONTROL STATION, enclosed on three sides by broken line 17, .includes a master controller, here represented by a combination of a SYSTEM SELEC- TOR or CYCLE SELECTOR, a VARIABLE FRE- QUENCY GENERATOR, 'a MOTOR DRIVE, VAJRI-V f ABLE SPEED VARIABLE FREQUENCY and a THREE PHASE SUPPLY. Included in the MASTER CONTROL STATION is la SYSTEM SUPERVISOR, the subject of the presentinvention.

It should be understood that the three phase supply may be an oscillator or three phase generator, for example, which generates a three phase electrical signal. In the preferred form the frequency of the three phase electrical signal is 400 cycles per second. However, it should be understood that such three phase signal is not limited to such frequency, as 'other frequencies may be employed, as desired.

The three phase, V400 cycle per second electrical signal is applied to the three phase system RF, including the network of coils RF', from the three phase supply. A three phase signal is induced into the network of coils VF byy the network of coils RF.

The network of coils RF is a stationary network and the network of coils VF is rotated by the motor drive so that the electrical signal in the system RF is a three phase 400 cycle per second signal, for example, and the induced electrical signal in the system VF is a three phase 400i Y cycles per second signal, for example, `according to the speed and direction of rotation of the network of coils VF', clockwise or counterclockwise, for example.

It should be understood that the system selector or cycle selector has an independent source of power and selects a system or cycle, respectively, according to demands of traffic as determined through tra'lc actuation.

A system selector may be of the type fully described in my` U.S. Patent No. 2,542,978, issued February 27, 1951, under the nameof Traic Actuated Control Apparatus. A cycle select-or may be of the type fully described in my U.S. Patent No. 2,288,601 issued J-uly 7, 1942 under the name of Tratiic Cycle Selector Apparatus. However, in lieu of a system selector or a cycle selector, a time clock or program timer may be used which may cause the variable frequency generator to vary its output, as desired.

The motor drive is mechanically connected to the neti work VF (illustrated by the broken line IS) and through suitable gearing (not shown) revolves the network VF' at a variable speed, as determined by the frequency of the input from the variable frequency generator, of the order of one revolution every 40 seconds producing a three phase signal of 400%@ cycles per secon-d to one revolution every 120 seconds producing a three phase signal of 4001/120 cycles per second, for example.

Gener-ally, the system selector or cycle selector selects an output according to the actuation of tratic and, as dcsired, controls the variable frequency generator thus controlling the frequency of the output of the variable frequency generator which frequency in turn controls the speed of the motor drive.

The Aline 15 from the VARIABLE FREQUENCY GENERATOR leading into the SYSTEM SUPERVISOR is illustrated as extending through a switch SW1 including terminal l and contacts `6l and 62.. The switch SW1 is illustrated as a manual switch for convenience. Closure of switch SW1 to make contact lbetween terminal 90 and contact 61, as illustrated, connects the output of the source of supply represented by a plus in a circle. V

One three phase system RF, including lines a, b and c anda second three phase system, VF, including lines d, e and f extend across the upper section of FIG. l. Both three phase systems are connected to each local controller in the traiic control system.

Within the master control stationthe SYSTEM SUPER- VISOR is connected to line a of the system RF and to lines d, e and f of system VF. The SYSTEM SUPER- VISOR is illustrated in a schematic circuit diagram in FIG. 2.

A line IC leads out of the SYSTEM SUPERVISOR and extends to the several local controllers in the traffic control system. f

A switch SW2, illustrated with terminal 96 connected to contact shown closed, applies power to the line IC.

The LOCAL CONTROLLER is illustrated in schematic blockrform with a relay X controlled by the line IC from the SYSTEM SUPERVISOR. The relay X controls contacts a', b', c', d', e and fto close the contacts when energized and also controls contact K, to open the contact when energized. When contacts a', b', c', d', e' and are closed and contact K is open the normal drive is connected to the three phase lines to operate the controller and the alternate drive is disconnected from its source of Supply. With contact conditions reversed the normal drive is disconnected from the three phase lines andthe alternate drive is connected to an external source of power to energize the alternate drive unit.

An example of one type of LOCAL CONTROLLER may be found in my said copending application Serial Number 510,926. s

Extending from the LOCAL CONTROLLER are two sets of three signals illustrated in an intersection. Only two sets of signals are illustrated for convenience although it will be appreciated that there may be one set of Y signals controlling each approach to the intersection. The.

Since the chart represents one complete cycle, conditions represented in the right edge of the chart, representing the end of one cycle, would be followed by conditions represented in the left edge of the chart, indicating the beginning of a cycle.

The horizontal lines to the right of each identifying number in the cam chart indicates that time in the cycle of the cam shaft when the cam contact is closed. Short vertical lines are placed at the closing and opening positions for emphasis.

Below the identifying cam numbers is the term PE- RIODS. Each cycle may be divided into periods, each single cycle including four (4) periods here called P1, P2, P3 and P4.

Period Pl, in the preferred form, is approximately seconds minimum duration, for example, to allow for initial warm-up of the tubes ofthe master controller when originally turned on. During this period the master controller is accorded opportunity to correct itself before any remedial action is taken by the system supervisor.

Period P2, in the preferred form, is somewhat shorter in time than period Pl but may be of the order of approximately l0 seconds minimum duration, for example.

Period P3 has a somewhat shorter minimum time period than P2. Period P3 need be long enough, in time, approximately 4 to 5 seconds, for example, to allow the motor M to come to a complete stop before the sequence of cam positions as shown for period P4 occurs. In order that the system supervisor move out of position P3 the normally closed reset button (56 in FIG. 2) must be pushed, as explained below.

Period P4 is a homing period to bring the system supervisor to the end of the current cycle and the beginning of the next cycle. During period P4 all cam contacts will be closed except cam contact A2-A3. Period P4 may be on the order of 4 to 5 seconds, for example.

The normal rest position of the cam shaft occurs in period Pil, immediately after termination of period P4, however the system supervisor may rest during any part of period Pl.

Since Pll may be a rest position, the time of P1 may be considered a minimum time with the maximum time undeterminable.

Period P2 may be lengthened in time since the motor may come to a halt when the cam shaft is in period P2 so that the time above approximated for period P2 is a minimum time. Although the system supervisor may stop in period P2 the period may not be considered a rest period. This will become apparent from the description below.

Period P3 is a stop position. The cam shaft may be rotated through positions Pl and P2 but during normal operation of the system supervisor, as explained more fully below, the motor is halted in period P3. In order that the motor be energized to move the cam shaft out of position P3 the reset button must be pushed, all as described below.

Period P4, the homing position, is a self-adjusting position where the system supervisor adjusts itself and moves into the rest position P1.

FIG. 2 is a schematic circuit diagram of the preferred embodiment of the system supervisor, the present invention. In the upper part of the diagram are two sets of three lines labeled RF and VF. These lines correspond to similarly labeled lines in FIG. l and are the two groups of lines extending from the master control station carrying the three phase 400 and 400+ cycles per second electrical signals developed by the master controller.

Below the three phase lines are three identical circuits, each circuit blocked oif with a broken line box and individually labeled B3, B2 and Bil.

Line a of the three phase line RF is connected to one side of the primary coil of each of the step-up transformers T3, T2, T1 while the other side of the primary coil is connected to one line d, e and f, respectively, of the three phase line VF.

It should be understood that the three phase system RF is at a constant frequency, of the order of 400 cycles per second, for example.

This three phase system is used as a reference line and reference frequency. The three phase system VF varies in frequency from 4001/ cycles per second to 400%() cycles per second for example, according to the speed of rotation of the network VF' as caused by the motor drive, as illustrated in FIG. 1, and is therefore shifting in phase with reference to the three phase system RF.

As generally described above, the system selector or cycle selector will cause the variable frequency generator to -vary the frequency of its output as desired. The motor drive varies its speed of rotation according to the frequency of the output of the variable frequency generator. Thus variation of rotation of the network VF' associated with the system VF `as driven by the motor drive, is obtained. One complete revolution of the net- Iworlr VF', in a clockwise direction, may be accomplished in from 40 seconds producing a frequency of 4001/40 cycles per second for example, to 120 seconds, producing a frequency of 40017420 cycles per second for example, thus there will be lcoincidence or an in-phase condition between voltages on lines RF and VF once every 40 second-s to once every 120 seconds, respectively, for example.

As the set of variable frequency lines d, e and f are constantly shifting in phase lwith respect to the reference frequency lines a, b, and c, an in-phase condition will occur between line a and line d at one time, between line a and line e when the variable frequency lines have shifted in phase by 120 degrees, and between line a and line f when the variable frequency lines have shifted by 240 degrees, and again between line a and line d when the variable frequency lines have completed one cycle of phase shift or 360 degrees.

The voltage between lines a and d, a and e, and a and f is applied to the primary windings of the transformers T3, T2 and T1 respectively. The voltage between lines a and f will be an alternating current voltage of the order of 400 cycles per second, for example, whose amplitude is varying at a very low frequency of the order of from 1/120 of a cycle per second to 140 of a cycle per second in accordance with the rate of the slow phase shift. The voltage of this low frequency component will be essentially zero when the in-phase condition exists and will increase in amplitude slowly, according to the length of the cycle, to a maximum voltage when the two lines have shifted in phase degrees, or are half a cycle apart, then will decrease towards zero as the inphase condition is again approached. The alternating current voltages applied to transformer T2, and transformer T3 will vary similarly, however, being displaced 120 degrees of 1/3 of a cycle of phase shift of the variable frequency lines VF, with respect to the reference frequency lines RF, and thus the in-phase or zero voltage conditions will occur 120 degrees apart from each other and from that applied to transformer T1.

Operation of monitoring circuit B1, which is typical of operation of monitoring circuits B2 and B3, will be described.

Transformer T1 serves as `an isolating and step-up transformer. The alternating Voltage in the secondary coil 22 of transformer T1 is rectified by half-wave rectifier tube 25. The negative portion of the wave causes current to pass between cathode 24 and anode 26. This current causes a negative direct current voltage to appear between point 27 and ground l23, across resistor 29.

Capacitor 30 essentially filters the 40()` cycle per second ripple from the load resistor 29. The time constant of this combination is such as to accurately follow the amplitude of the input signal of transformer T1, thus providing a D.C. signal across capacitor 30 varying in amplitude in the same manner as the low frequency component of the A.C. signal in the primary coil of transformer T1.

The differentiating network,.consisting of capacitor 3d and resistor 32, has applied to it the varying D C. voltage which appears across capacitor'36'. The voltage across resistor 32 results from the charging or discharging of capacitor 31 as the applied voltage changes, and will be of an amplitude proportional to the rate of change of the applied voltage and of a polarity correspending to the direction of change. That is, if the applied voltage is increasing rapidly in a negative direction the voltage across resistor 32 will be a high value of negative polarity with re-spect to ground and if the applied voltage is decreasing rapidly from a negative value, the output voltage across resistor 32 will be a high value of positive polarity with respect to ground.

This output voltage from the differentiating network is applied to cathode 33 of diode 34.

Similarly circuits B2 and B3 produce voltages at the cathodes of their output diodes, the voltages reaching f This will occur in circuit lBl. as reference line a is in phase withline f, in circuit B2 as reference line a is in phase with line e `and in circuit B3 as reference line a is in phase with line d.

As the voltages in the individual lines d, e, and f of the three phase system VF, vary in phase with respect to the reference line voltages in a cyclic manner at a rate of from 40 seconds per cycle to 120 seconds per cycle, lfor example, the in-phase conditions between line a of the three phase system RF, and each of the lines d, e and f of the three phase system VF, will occur 1/3 of this cyclic rate apart, that is every 131/3 seconds per cycle to every 40' seconds per cycle, corresponding to a 40 second cycle t0 a 120 second cycle, respectively, for example.

Therefore, as the voltages applied to the cathodes of the youtput diodes of circuits Bl, B2 and B3 reach their maximum amplitudes 1/a of a cycle apart, the diodes individually will pass current for the 1/3 of the cycle when the voltage at the cathode is of a higher amplitude in a negative polarity than the other two output cathodes and the voltage appearing at the anodes, which rare connected in parallel, will be of a negative polarity and of 'an amplitude corresponding to the maximum negative portions of the three cathode voltages.

This voltage appears across diode load resistor 36 and causes this negative Voltage to be applied to grid 38 of the tube 39 and holds the tube 39 at cutoif.

Considering operation of one monitoring circuit independent of the other monitoring circuits, the output of the tube section 34 of circuit Bll, for example, would vary from a low negative output voltage to a maximum negative output voltage to a low negative output voltage during the 180 degree phase shift of VF with respect to RF. The equivalent tube section in circuit B2 produces a similar varying outputvoltage during 180 degrees of the phase shift of the two three phase systems and the equivalent tube section in circuit B3 will produce a similarly variable output during 180 degrees phase shift of the three phase systems, each output reaching a maximum value 120 degrees of the phase shift cycle after the preceding circuit voltage. Thus during one period of the phase shift between the two three phase systems a varying D.C. will be produced across resistor 36 which will correspond to the` larger of the negative peaks of each output voltage from B1, B2 and B3, which voltage peaks are displaced 120 with respect to each other. The resultant voltage across resistor 36 is a high D.C. voltage with a third harmonic ripple; the minimumvalue 3 of which is always greater than the cut-oil? value of the tube 39.

Resistor 36 is connected in common to the anodes of the isolating diodes of each monitoring circuit, and provides a high resistance return for the diode circuit.

The voltage drop across resistor 36 is minus at the end connected to the anode 35 of tube section 34 and the grid33 of tube 39, and is of sucient magnitude to maintain the tube 39 cutoff so long as the monitoring circuits B1, B2 and B3 sequentially produce the individual outputs.

With the triode 39 cut-off the relay F is held deenergized. The circuit through which the relay F is energized may be traced from a DC. source, represented by a plus in a square through the coil of relay F, anode 46, cathode 41 of tube 39 to common ground 23.

With relay F deenergized as presented, its contacts 42 and 43 are closed and 44, 45 and 46 are open.

Relay R is presented energized with its contact 49 closed and its contact 50 open. Relay R is held energized through its own lock-in contact 49. The circuit may be traced from volt A.C. power source, represented by a plus in a circle through leads 51, 52 and 53, the coil of relay R, leads 54 and 55, contact 49, normally closed reset button 56 to ground 23.

The motor M is presented as stopped with cam contacts A2-A3 closed, Alf-A2 open, Bib-B2 closed, Cl- C2 open and D1-D2 closed. This condition indicates that the motor M is stopped with the cam shaft in the rest period P1.

Relay N, presented as energized, attracts and closes its contacts 59, 6l) and 6l and opens its contacts 62, 63 and 64. Relay N is held energized through a circuit that may be traced from the 120 volt A.C. supply through leads 51 and 65, the coil of relay N, leads 66 and 69, cam contacts Bl-BZ to ground 23. A lock-in circuit is also completed from the junction of leads 66 and 69 through contact 60, lead '70, contact 43 to ground 23.

Relay L is also presented energized with its contacts 73, 74 and 75 closed and 76 and 79 open. The energizing circuit of relay L may be traced from the 120 volt A.C. supply through lead 5l, the coil of relay L, leads 71 and '72, cam contacts Dig-D2 to ground 23. A lock-in circuit is also completed from the junction between leads 71 and 72 through contact 74, lead 86, contact 4-2 to ground 23.

Let it be assumed that a failure occurs in a part of the master controller so that suchy failure causes the motor drive to stop. With the motor drive stopped rotation of the network VF ceases and the frequency of the three phase system VF will be continuously the same as the frequency of the three phase system RF, that is 400 cycles per second, for example. With both three phase systems having the same frequency, the progressive shifting of phase between the two systems will cease.

The monitoring circuits Bl, B2 and B3 will sense this steady phase relation between the two three phase systems in that the voltage across'lines d, e and f of the system VF with respect to line a of the three phase system RF, that is the voltages between lines a and d, a and e and a and fwill be constant rather than varying so that the capacitor 3l of circuit Bl and its equivalent capacitors in B2 and B3 of the respective differentiating circuits will effectively block passage of the curent and no voltage drop will appear across resistor 36. With no voltage drop across resistor 36 there is no negative bias applied to the grid 38 of tube 39 sothat tube 39 passes current to energize relay F through the circuit previously traced.

With relay F energized contacts 44, 45 and46 are closed and contacts 42 and 43 are opened. Closure of contact 44 completes a circuit from the A.C. supply through lines 51 and 52,A motor M, lines S1 and 82, contact 73, line 83, contact 44 to ground 23 to cause motor M to rotate ythe cam shaft out of its rest period P1 toward and into period P2.

Closure of contact 46 completes a circuit from the A.C. supply through line 5l, indicator lamp L1, contact 46 to ground, to illuminate the lamp L1 which may be used to indicate a failure has developed in the monitored equipment.

Closure of contact 45 completes a circuit that may be used to energize an audio alarm or sound device from an A.C. supply through lines 84, 85 and 86, contact 45, an alarm represented by a rectangle labeled 89, to ground. Such audio alarm may be any buzzer, bell or gong type device designed to produce an audible sound upon completion of a circuit in which it is placed.

Contact 43 opens to break the holding circuit for the relay N but since cam contacts Bl-BZ are closed the relay N remains energized through a circuit previously described.

Contact 42 opens to break the holding circuit for the relay L but since cam contacts D1-D2 are closed the relay L remains energized through a circuit previously described.

The motor M will rotate the cam shaft and when the cam shaft reaches the period P2 of the cycle the cam contacts B1 B2 will open to cause relay N to drop out.

Deenergized relay N releases and opens its contacts S9, 60 and 61 and releases and closes contacts 62, 63 and 64. Opening of contact 61 and closure of contact 62 changes the current supply to terminal 90 from supply 91 to supply 92. Closure of contact 63 illuminates lamp L2 via a circuit from the A.C. supply through line 84, lamp L2, contact 63 to ground 23.

Closure of contact 64 completes a circuit to sound an auido alarm through a circuit that may be traced from the A.C. supply through line 84, contact 64, audio alarm 93 to ground 23.

The terminal 90 represents an input to the motor drive, through line 16 as shown in FIG. 1. The power supply may be from a source through terminal 91 and Contact 61 or through terminal 92 and contact 62 depending upon which contact 61 or 62 is closed. The two position contact 61/62 in FIG. 2 is illustrated in FIG. 1 as a switch SW1 with contacts 61 and 62.

As presented the power source through terminal 91, and contact 61 to terminal 90 is derived from the Avariable frequency generator while the power source through terminal 92 and contact 62 to terminal 90 is an alternate source of power, all as shown in FIG. 1.

The shift in the source of power as made by operation of the double contact 61/62 of relay N, or switch SW1 in FIG. 2, is in the nature of a test to determine the general location of any failure with reference to the contact 61/62, or as shown in FIG. 1, switch SW1. If the failure indicated by lack of rotation between the two three phase systems is in the variable frequency generator, the system selector or cycle selector, or their associated units below line 15, as shown in FIG. l, then closure of contact 62 to complete the alternate source of power through terminal 92 to terminal 90 would apply the alternate source of power to the motor drive to start the motor which would again rotate the network VF. With the network VF again rotating the voltages across the lines d, e and f will vary with respect to line a of the system RF as the two three phrase systems shift in phase with respect to each other.

The alternate source of supply through contact 62 and terminal 92 may be a xed cycle alternating current, for example, 60 cycle A.C. which will drive the variable speed motor drive at a pre-determined speed to produce a fixed 8() second cycle, for example. The alternate source of power may also be another variable frequency generator, for example.

If the failure had occurred below the contact 61, that is in the variable frequency generator or its associated units, then application of the alternate power supply to 10 the motor drive, through contact 62 and terminal 90 will restore rotation of the network VF thus restoring variation of voltages between the lines of the three phase system VF and the line a of the three phase system RF.

The voltage variation across the input coils of the respective transformers would result in the respective monitoring circuits producing a voltage across resistor 36 and increasing the bias of tube 39 to cut-olf thus causing relay F to become deenergized.

With relay F now deenergized contact 44 would open the energizing circuit for the motor M so that the motor M would stop rotating the cam shaft. Contact 45 would open to break the circuit energizing the audio alarm 89 and contact 46 would open extinguishing the lamp L1 indicating there is again rotation between the two three phase lines.

With the motor M stopped and both relays F and N deenergized the indicator lamp L2 would remain illuminated and the audio alarm 93 wouldy continue to sound to indicate that the alternate source of power is applied to the motor drive through terminal 90. This also indicates that a failure has occurred somewhere in the equipment shown below the contact 61 in FIG. l.

The motor M would remain stopped holding the cam shaft in period P2 until the reset button 56 is pushed to cause the motor to drive the cam shaft through periods P2, P3 and P4 to come to rest again in period P1 or until variation of one or more of the voltages stops again to cause energization of the relay F which in turn causes energization of the motor to drive the cam shaft to period P3.

Momentarily, let it be assumed that application of the alternate source of power has restored phase shift between the two three phase systems which phase shift is sensed by the monitoring circuits which in turn cause the motor M to stop with the cam shaft in period P2 and with lamp L2 illuminated and audio signal 93 soundlng.

Let it also be assumed that the failure has been noted and repaired and it is now desired to return the system supervisor to its originally assumed condition. This may be accomplished by pushing the reset button 56 to cause deenergization of relay R. Deenergized relay R opens contact 49 and closes Contact 50. Closure of contact 5t) completes a circuit to drive the motor M from the A.C. supply through leads 51 and 52 the coil of motor M, contact 50, cam contact A2-A3 to ground 23. This circuit will hold and cause the motor to drive the cam shaft through the remainder of period P2 and into and through period P3. In period P3 cam contact D1-D2 in the relay circuit will open but relay L is held energized by closure of contact 42 by deenergized relay F thus permitting travel of the cam shaft through period P3 without causing deenergization of relay L and the resulting release of master control over the local traffic controllers in the traic control system.

In period P4 cam contact A2-A3 will open to break the circuit driving the motor M but closure of cam contact Bl-BZ causes energization of relay N from the A.C. supply through leads 51 and 65, the coil of relay N, leads 66 and 69, cam contact B1-B2 to ground 23. Energized relay N causes closure of contact 59 which completes an energizing circuit for motor M through cam contacts C1- C2 the circuit may be traced from the A.C. supply through leads 51 and 52, the coil of motor M, lead 81, contact 59, cam contact CIL-C2 to ground 23.

The last described circuit will cause motor M to drive the cam shaft through period P4 and into period P1 where cam contacts C1-C2 and A1-A2 will open, and cam contact A2-A3 will close. When cam contacts A1A2 closed in period P4 the relay R became energized from the A.C. supply through leads 51, 52 and 53, the coil of relay R, lead 54, cam contact A1-A2 to ground 23. Energized relay R then locks in over its own contact l49 from the A.C. supply through leads 51, 52

1 l and 53, the coil of relay R, leads 54 and 55, contact 49, reset button 56 to ground 2.3. The opening of contact permits the motor M to become deenergized as soon as 4the'ca-m shaft enters period P1 and opens cam Contact Cl-CZ. Thus the system supervisor is returned to its originally assumed rest condition in period P1.

If a failure in the master controller is located in the variable frequency motor drive, or in the networks RF or VF', or in the three phase supply or the associated three phase lines the lalternate source of power through contact '62 to terminal 99 would not cause voltage variations between the three phase lines. The monitoring circuits El, B2 iand B3y individually would continue to withhold a voltage from iacross the resistor 36 andthe Itube 39 will keep passing current. The relay F lwill remain energized so that the lamp Ll will remain illuminated and audio alarm l89 will continue to sound thus indicating a failure is still preventing vector rotation. The energizing circuit circuit for the motor M lwill remain closed through contact 44 so that the motor will continue to rotate the cam shaft through period P2.

Since relay N is iheld deenergized the lamp L2 will remain illuminated, the audio alarm 93 will remain sounding and the alternate source of supply will remain connectedto the motor drive.

As previously described, the contact 42 is heldV open by relay F and when the cam shaft rotates into period P3 cam contact Dl-DZ will open to cause deenergization of relay L. Relay L twill open contact 73 to break the energizing circuit for the urnotor `M and the motor will stop, holding the cam shaft in period P3. Contact 76 will ybe closed to energize an audio alarm 94 from the A.C. supply through line '84, line 85, contact 76, audio alarm 94 to ground 23. lContact '79 fwill close to illuminate the lamp L3 from the A.C. supply through lines `84, `85, lamp L3, contact 79 to ground 23. `Contact 75 will open to break `the circuit between terminals k95 and 96, and, as in `the assumed case, open the circuit energizing the relay X in the local controller, as seen in FIG. 1.

The opening of Contact 75, in the SYSTEM SUPER- VISOR, causes relay X, in the LOCAL CONTROLLER, as seen in FIG. l to become deenergized rand contacts a', b', c', d', e and f' yare released `and opened as contact K is released and closed. Closure of contact K supplies a local source of power to fan alternate drive in the local controller to drive the controller independent of the master control station outputs.

Thus the local con-troller would be operating independent of the master control station with the system supervisor maintaining motor M stopped and relays F and R energized and relays N and L deenergized.

The indicator lamp L3 and audio alanm 94 lwould be illuminated and sounding respectively, Ito indicate the line IC (as seen in FIG. l), through terminal 96, is deenergized.

The present condition of the system supervisor indicates la failure exists in the master controller (lamp L1 illuminated and audio alarm 89 sounding); that an alternate source of supply is being fed to the MOTOR DRIVE of the lmaster controller (lamp` L2 illuminated and audio alarm 93 sounding); that the failure was not remedied by applying an alternate source of supply; that the `failure is not limited to either the variable frequency generator or its input mechanism land that the local controllers are operating independent of the master control station, (lamp L3 illuminated and audio alarm 94 sounding).

The system supervisor will remain in its present condition until reset button 56 is manually pushed and is opened which would cause relay R to become deenergized. With relay R deenergized contact Sil is closed, completing an energizing circuit for the motor M as previously described. 'l`ihe motor M will rotate the cam shaft out of period P3 and into period P4 so that cam Contact A12-A3 will open and cam contacts A1A2, B1--B2, Cl-CZ and Dl-DZ will close.

through a circuit previously described.

Closure of cam contact B1-B2 will energize relay N Vfrom the A C.V supply through llines 51, 65, the coil of relay N, lines `66 and 6.9, cam contacts Bl-BZ to ground 23.

Closure of cam contact C1-C2,with closure of contact 59 by energized relay N, energizes the motor M through a circuit previously described.

Closure of cam contact D1-D2 will energize relay L through a previously described circuit.

It should be assumed that before reset button 56 is pushed to open the holding circuit lfor relay R, the master controller has been repaired.

If a failure still exists in the master controller the system supervisor ywill indicate the presence of such failure and advance through a pattern of operation -according to what section of the master controller the failure is located.

If the failure in the master controller has been repaired the system supervisor will again sense the lvector rotation between the two three phase lines and cutoff passage of current through tube 39. The system supervisor maintains relays R, N and L energized, relay F deenergized and rotates the cam shaft to period P1, the assumed original condition and there opens cam contacts Al-AZ and Cl--CZ and closes cam contacts AZ-AS.

vThe motor stops and the system supervisor maintains its monitoring of the three phase lines VF against line a of three phase lines RF. y

It should be understood that the audio alarms may or may not'be used in conjunction with'the indicator lamps, as desired.

It was Iabove assumed that rotation of the network y VF of the three phase line VF stopped s@ that rotation between the three phase lines stopped completely. It

should be noted-that a voltage applied :across one of Y the transformers of one of the monitoring circuits may drop or be lost altogether so that the effected monitoring circuit fails to develop la voltage drop across resistor 36 during the 1/3 of the period `of non-coincidence that the monitoring circuit would normally develop a voltage across such resistor. v

Should this occur the system supervisor would sense such loss of rotation during the 1/3 of the period of non-coincidence and causerelay F to Ibecome energized. If the 1/3 of the period of non-coincidence should not exceed the Atime necessary for the motor M to rotate the cam shaft through period P1 and into period P2 to Vopen cam contacts Bl-BZ then the Vmotor M will stop: in its period P1 and continue during the next succeeding equivalent 1/3 period of non-coincidence to rotate the cam shaft to period P2 to open cam contact Bl-B2.

Since there is rotation between the two remaining lines of the three phase lines VF and the reference line a of the three phase lines RF a voltage drop will app-ear across resistor 36 during the remaining 2/3 of the period of non-coincidence so Vthat the tube 39 will not pass current during 2/3 of each period of non-coincidence while the cam shaft remains in period P1.

If when the cam shaft is rotated into period P2 the failure is remedied the system supervisor will drop out relay F and hold lamp L2 illuminated, audio 'alarm 93 sounding and will complete the alternate current supply 92 to terminal 90 Via contact 52.V

If the failure of the one line is not remedied when the earn shaft is rotated into period P2 then the relay F will become energized during that portion of the cycle that the monitoring of such failed line takes place. During such monitoring period the motor M will cause the cam shaft to revolve. f

I'f, on the other hand, the failure of rotation still exists then the system supervisor will rotate its cam shaft during succeeding equivalent 1/3 period of non-coincidence until thecam shaft reaches its period P3 and causes the local controller to reject control from the master controller and operate independent of the master controller.

Although the description above has been presented with the line a of the three phase system RF -used as a reference line from which to `detect rotation of the individual lines d, e and f of the three phase system VF, -it is obvious that the line b or line c may be used in lieu of line a.

As presented each of the lines d, e and f are individually monitored, with respect to the line a with monitoring circuits designed `to respond to the negative portion of the variable D.C. If a more critical response, and under certain conditions a more rapid response, to a failure is desired, three additional monitoring circuits may be employed, substantially similar to those described above, except that the additional monitoring circuits would be designed to respond to the positive portion of the variable D.C. by inverting diode 24 in the three additional units.

This would increase the level of the low voltage between the peak voltages land reduce the displacement of peak voltages from a 120 `displacement to a 60 displacement between voltage peaks.

Since the three monitoring circuits apply their individu-al outputs across the resistor 36 sequentially, it may occur that a failure may develop, either by an open or a short in the line e, of the three phase system VF, for example, while the monitoring circuit Bl is applying its output to the resistor 36 from the input voltage between lines aand f.

Should such failure occur the failure would not be indicated by the system supervisor until that part of the cycle when the circuit BZ, monitoring the voltage between lines a and e is applied to its output to the resistor 36.

It may be desired to reduce the sensitivity of the system supervisor to a momentary failure or failures when such momentary failure or failures develop in the line monitored by the monitoring circuit then applying its output to resistor 36.

Reduced sensitivity may be desired to reduce possible immediate reaction to momentary shorts, opens or other momentary failures in the master controller or its output lines, such as may be caused by servicemen when checking various par-ts of the master controller or its output lines, for example.

To obtain such reduced sensitivity the failure relay F may be made a delayed action relay, with the delay upon energization. By delaying the reaction of the .relay F, although a failure may be immediately sensed by the monitoring circuits, the failure must continue for a short period in order to energize -relay F. If between the time such failure develops and the relay F becomes energized the failure condition terminates, then such failure, although sensed in the monitoring circuit monitoring the line in which the failure occurs, will not be sensed by the relay network of the system supervisor due to the delayed reaction of relay F.

It is obvious that should momentary failures develop in any line that is monitored by a circuit not then applying its output to the resistor 36 such momentary failure would not be indicated by energization of relay F if the failure condition is corrected before the monitoring circuit then sensing such failure applies its output to the resistor 36 in clue course of operation as described above.

Although the present invention has been described with reference to the monitoring of polyphase, and in particular three phase electrical systems, such description is not to be construed as limiting the invention only to such systems, the present invention may `also be -applied to monitoring more or less than three phases by increasing or reducing accordingly the number of voltage difference monitoring circuits employed, and particularly in the case otE less than three phases, by introducing some carryover or time lag in the part of the sensing circuit involving tube 39 and relay F for example. Thus, lfor example a capacitor may be employed across resistor 36 to sustain the bias on tube 39 during normal cyclic blank periods between voltage pulses from the individual voltage difference monitoring circuits, or a capacitor may be placed across the coil of relay F or other well-known means employed for introducing a delayed action in energization of relay F.

Although some modifications of the present invention have been described it will be obvious to those skilled in the art that other changes in form, `arrangement and connection of the various elements and substitution of equivalent components may be made without departing from the spirit of the invention within the scope of the appended claims.

yI claim:

l. In a master control sys-tem for controlling local traffic signal controllers cyclically by slow progressive phase shift between periodic` electrical wave energies, and having a polyphase differential generator including two polyphase windings one of which windings is supplied with polyphase electrical energy and the second of Which windings derives a second polyphase energy shifting progressively in phase with respect to the first at a rate proportional to the speed of relative rotation between said windings, and said system having means for normally rotating one of said windings relative to the other -for providing said slow progressive phase shift -at la desired rate, auxilary means .for so relatively rotating said windings at a desired rate when operating, means for sensing and providing distinguishing response for said progressive phase shift and cessation of said progressive phase shift, respectively, for monitoring said phase shift and means for operating said normal means for rotating said windings in response to continued sensing of said progressive phase shift by said sensing means and for operating said auxiliary means for rotating said windings in response to sensing of cessation of progressive phase shift by said sensing means.

Z. A combination as in claim l in which said operating means includes a cyclic switching means initiated in its cycle by said sensing means sensing cessation of progressive phase shift to so switch from said normal operating means to said auxiliary operating means in one part of its cycle and :to release the local controllers from control by the master controller in a yfurther part of said cycle to permit said local controllers to operate independently of said master controller if cessation of progressive phase shif-t continues after the first said switching action.

3. A combination as in claim 2` and including means 'for holding said cyclic switching means in said one part of its cycle in response to said sensing means sensing said progressive phase shift again after said switching to operation of s-aid auxiliary operating means, and reset means for interrupting said holding means and for returning said cyclic switching means to normal inactive condition for switching back from said auxiliary operating means to said normal operating means.

4. A combination as in claim 3 and including means controlled by said sensing means for indicating such cessation of progressive phase shift.

5. A combination as in claim 4 and including means controlled by said switching means for indicating when said auxiliary operaitng means is so operating.

6. A combination as in claim 5 and including means controlled by said cyclic switching means for indicating when said local controllers are so released in said further part of said cycle.

7. In a master control system for controlling local trafiic signal controllers cyclically by slow progressive phase shift between periodic electrical wave energies and normally providing outputs of said wave energies in the form of two polyphase wave energies having such relative phase shift for such control, the combination including means for deriving difference voltages between a phase l of one of said polyphase outputs and the phases of the other polyphase output and said voltages varying cyclicaln ly with said progressive phase shift, differentiating circuit means responsive to said cyclic variation for deriving further voltages from said difference voltages, combining means for combining said `further voltages and voltage lresponsive means including a relay controlled by said combined further voltages tto respond to cessation of any of said combined further voltages.

8. In ya master control system for cyclically operating local traic signal controllers by slow progressive phase shift, a master controller having two sets of polyphase output lines providing polyphase electrical outputs one of which has such slow progressive phase shift in relation to the other for so operating said local controllers, means connected between iat least one line of one of said sets and .the respective lines of the other of saidvsets to derive respective difference voltages therefrom, detector circuits individual to the respective last named means to derive respective direct current voltages varying slowly cyclic-ally 'with sia-id progressive phase shift, differentiating circuits individual to the respective detector circuits for deriving Y further respective direct current voltages therefrom varying in accordance with the rate of change thereof, rectifying circuits for rectifying said further respective voltages, and circuit means combining the several rectified voltages in parallel in the same polarity to provide a resultant voltage representing at all times the largest of the individual voltages, and voltage responsive means including an electrical translating device and controlled by said :resultant voltage.

9. A combination las in claim l in which said operating means includes Ia cyclic switching means initiated in its cycle by said sensing means sensing cessation of progressive phase shift to so switch from said normal operating means to said auxiliary operating means in one part of its cycle -and to release the local controllers from control by the master controller in a further part of said cycle to perm-it said local controllers to operate independently of said master controller if cessation of progressive phase shift continues after the first said switching action, and means for holding said cyclic switching means in said one part of its cycle in response to said sensing means .sensing said progressive phase shift again after said switching to operation of said auxiliary operating means, and means for continuing said cyclic switching means to said further part of its cycle and holding said cyclic switching means in said-further part of its cycle in response to continued cessation of said progressive phase shift in said one part of said cycle, and reset means for interrupting said holding means in said one part and in said further part of said cycle for returning said cyclic switching means to normal inactive condition for switching back .from said auxiliary operating means `to said normal operating means'and to restore said local controllers to con- Ltrol by said master controller.

l0. A combination yas. in claim 8 in which Ysaid volt- :age responsive means includes an electronic tube having .a conduction circuit controlled by `a `grid normally biased :to cut-olf by said resultant voltage and becoming conducting by reduction of bias by reduction in said resultant `voltage from` any cessation of any of said difference voltvage, and said electrical translating device being conone of which has ksuch slow progressive phase shift in relation to the other for so opera-ting said local controllers, means connected between at least one line of one of said sets and the respective lines of the other of said sets to derive respective difference voltages therefrom, detector circuits individual to the respective last named means to derive respective direct current voltages varying slowly cyclically with said progressive phase shift, differentiating circuits individual to the respective detector circuits for deriving Ifurther respective direct current voltages therefrom varying in accordance with the rate of change thereof, said further respective direct current voltages partially overlapping each other in time sequence such that in each cycle of phase shift some of such voltages will be present normally, `and means controlled by said further respective voltages land including an electrical translating device having one condition in response -to presence of said further voltages in normal partially overlapping sequence and having another condition in response to cessation of lany of said further respective voltages.

l2. In a master control system for cyclically operating local traffic signal controllers by slow progressive phase shift, a master controller having two sets of polyphase output lines providing polyphase electrical outputs one of which has such slow progressive phase shift in relation to the other vfor so operating said local controllers, means connected between .at least one line of one of said sets and the respective lines of the other of said sets to derive respective difference voltages therefrom, detector circuits individual to the respective last named means to derive respective direct current voltages varying slowly cyclically with said progressive phase shift,

differentiating circuits individual to the respective detector n circuits for deriving further respective direct current voltages therefrom varying in accordance with the rate of change therof, means including an electrical translating device and controlled by the several said voltages to respond to cessation of any of said direct current voltages.

13. In a master control system for cyclically operating local traffic signal controllers, a master controller having a periodic electrical wave energy output and a polyphase periodic electrical wave energy output and means normally operating for slowly progressively shifting in phase said polyphase output lwith respect to the first mentioned periodic wave energy for so cyclically controlling said local controllers, auxiliary means normally ineffective but operable when effective for so progressively shifting in phase said polyphase output relative to the other output and means associated withV said master controller for sensing both said wave energies to provide electrical signals slowly varying in amplitude 'with said slow progres- -sive phase shift `and for responding to cessation of variation in amplitude of' said signals for switching from said normal means to said auxiliary means to make the latter effective in place of said normal means for providing said progressive phase shift.

14. A combination as in claim 13 -and including means for indicating when said auxiliary means is made so effective in place of said normal means, and means controlled by said sensing means :for indicating 'whether said progressive phase shift is resumed upon said auxiliary means being made so effective.

l5. 'In a master control system for cyclically operating local traffic Isignal controllers, `a master controller having a periodic electrical wave energy output and a polyphase periodic electrical -wave energy output land shifting means normally `operating for slowly progressively shifting in phase saidlpolyphase output with respect to ythe first mentioned -periodic fvvave energy and for cyclically controlling said local controllers, auxiliary shifting means for progressively shifting in phase said polyphase output relative to the other output, sensing means associated with said master controller for sensing said slow progressive phase shift and for responding to cessation of said progressive phase shift, cyclic switching means controlled by said sensing land cessation responsive means and having la cycle of operation including an initial position for so operating said normal means alud making so normally ineffective said auxiliary means `and a second position for switching from said normal means to said auxiliary means 1 'to make the latter effective in place of said normal means for providing said progressive phase shift, and means controlled by response to cessation of phase shift by said sensing and cessation responsive means for operating said cyclic switching means from said initial position to said second position.

16.v A combination `as in claim 15 and in which said switching means is so operated to its said second position only in response to such response to cessation of phase shift for 'a predetermined time.

References Cited in the le of this patent UNITED STATES PATENTS Zvorikin Dec. 4, 1900 Lomax July 15, 1941 Adler NOV. 3, 1942 Simon July 29, 1947 Johnson Aug. ll, 1953 Alles Jan. 5, 1954 Barker June 20, 1961 

1. IN A MASTER CONTROL SYSTEM FOR CONTROLLING LOCAL TRAFFIC SIGNAL CONTROLLERS CYCLICALLY BY SLOW PROGRESSIVE PHASE SHIFT BETWEEN PERIODIC ELECTRICAL WAVE ENERGIES, AND HAVING A POLYPHASE DIFFERENTIAL GENERATOR INCLUDING TWO POLYPHASE WINDINGS ONE OF WHICH WINDINGS IS SUPPLIED WITH POLYPHASE ELECTRICAL ENERGY AND THE SECOND OF WHICH WINDING DERIVES A SECOND POLYPHASE ENERGY SHIFTING PROGRESSIVELY IN PHASE WITH RESPECT TO THE FIRST AT A RATE PROPORTIONAL TO THE SPEED OF RELATIVE ROTATION BETWEEN SAID WINDINGS, AND SAID SYSTEM HAVING MEANS FOR NORMALLY ROTATING ONE OF SAID WINDINGS RELATIVE TO THE OTHER FOR PROVIDING SAID SLOW PROGRESSIVE PHASE SHIFT AT A DESIRED RATE, AUXILARY MEANS FOR SO RELATIVELY ROTATING SAID WINDINGS AT A DESIRED RATE WHEN OPERATING, MEANS FOR SENSING AND PROVIDING DISTINGUISHING RESPONSE FOR SAID PROGRESSIVE PHASE SHIFT AND CESSATION OF SAID PROGRESSIVE PHASE SHIFT, RESPECTIVELY, FOR MONITORING SAID PHASE SHIFT AND MEANS FOR OPERATING SAID NORMAL MEANS FOR ROTATING SAID WINDINGS IN RESPONSE TO CONTINUED SENSING OF SAID PROGRESSIVE PHASE SHIFT BY SAID SENSING MEANS AND FOR OPERATING SAID AUXILIARY MEANS FOR ROTATING SAID WINDINGS IN RESPONSE TO SENSING OF CESSATION OF PROGRESSIVE PHASE SHIFT BY SAID SENSING MEANS. 